The present invention relates to beamforming. In particular, ultrasound signals from a patient are beamformed to provide values representing one or more spatial locations.
Acoustic energy is transmitted as an acoustic beam into a patient. Echoes are received and transduced to electrical signals. The received signals are relatively delayed and apodized. The delayed and apodized signals are then summed together. The summed value represents a spatial location along a receive beam. By altering the delay and/or apodization profile as a function of time, a plurality of beamformed values representing a line or beam are formed in response to a given transmission. To scan a two or three dimensional region, the process is repeated along a plurality of different scan lines. The scan process may be increased by transmitting and/or receiving a plurality of separate beams at a same time.
To increase the scan rate, a plane wave covering a large region of the patient is transmitted. A plurality of receive beamformers are used in parallel to form receive beams along different scan lines in response to the same transmit. Alternatively, a Fourier transform is applied to the data received at each element of an array over time. After processing in the frequency domain, an inverse transform generates data representing the different locations in the scanned region. For example, see U.S. Pat. No. 6,685,641, the disclosure of which is incorporated herein by reference. A temporal Fourier transform is applied to radio frequency echo signals from each element. The signals are then phase rotated. A spatial Fourier transform is then applied, followed by a complex interpolation. An inverse spatial-temporal Fourier transform provides the image data.